Evaluation of the Suitability of Agriglasses Containing ZnO for Plant Fertilization

Six different samples from borosilicate and phosphate glassy systems have been synthesized. Glass batches were prepared from chemically pure materials and melted in platinum or porcelain crucibles and at temperatures in the range 1,000–1,450 °C for 2-3 h until homogeneity was reached. The prepared specimens were annealed at the appropriate temperatures of 380 or 520 °C for the phosphate and borosilicate glasses, respectively. Samples of 2 mm dimensions were tested for dissolution behavior in 2% citric acid solution for 1, 2, 3, and 4 weeks and the released phosphorous and potassium ions (macroelements) and zinc ions (microelement) were measured. Also, Infrared (IR) absorption spectra of the samples were measured before and after immersion in the leaching solution. The experimental results indicate that the release of the macroelements and microelements depends primarily on the composition of the agriglass and the percent of constituent ions and the released ions vary slightly from 1 week to 4 weeks. The IR spectra show characteristic IR absorption bands due to vibrations of collective silicate, phosphate, and borate groups, depending on the agriglass composition and the chains or units seem to be interconnected with each other within the glass network. The interpretation of the dissolution behavior is based on a suggested mechanism for the release of the easily soluble components from the glass specimens. The IR absorption spectra support and confirm the proposed behaviour for the corrosion mechanism.